[ovs-discuss] One NIC -- one bridge only?

[Ben Pfaff]

On Sun, Jul 12, 2015 at 04:17:20PM +0530, Abhishek Verma wrote:
> I am running OVS inside a VM. I have only one virtual NIC from which i can
> receive traffic. I was trying to do something wherein i create different
> GRE tunnels terminating at different VMs based on the result of some
> classification done on the incoming packets. You can imagine that i have
> packets belonging to different sessions that need to be identified and sent
> to a different GRE tunnel.
> 
> Given that i have only one NIC from which i can receive packets, i can only
> create one bridge right? I say this because its only the bridge in which i
> have added this virtual NIC that i will be able to receive packets. I need
> to do whatever classification i want inside this bridge and send packets
> out on different GRE tunnel ports.
> 
> I will however have to be very careful in doing this since all traffic by
> default will be flooded to all ports of the bridge. And hence, if i am not
> very careful with my flow rules, then i will leak traffic from one session
> to the other.

GRE tunnel ports don't need to be on (indeed, ordinarily should not be
on) the same bridge as the port that carries the encapsulated traffic.
Thus, you can spread the GRE tunnel ports among as many bridges as you
like.